THE QUALITY of Soviet medicine is a peculiarly emotional issue, as if it were the ultimate measure of Marx's economic promises. My earliest and fiercest argument in Moscow was on the subject. Dr. Yelena Bonner, wife of Andrei Sakharov, was railing at medical services there, based on her experiences as physician and patient. I was skeptical, which made her angry.

"At least it's free," I said finally, trying to escape the uncomfortable role of defender of Soviet medicine.

"It's not good and it's not free either," she insisted. I thought at the time that she was unwilling to concede even that point because she so despised the political system. But she was right. There is a "gray market," to put it most benignly, for doctors' services, nurses visits, and drugs. Only its size is in dispute.

Even Dr. Sanya Lipavsky, the "dissidents' doctor" who turned out to be a KGB plant (and betrayed Anatoly Scharansky), spoke fiercely about the "scandal" of Soviet medicine.

Neither I nor any other Western correspondent wrote much on the subject, however. In part, dissident horror stories were suspect, as well as anecdotal and isolated, while the "average Russian" does not tell his woes to foreigners. Personal experiences also sometimes contradicted such accounts; our 6-year-old son, who had a minor concussion, received fast and excellent treatment at a Moscow hospital. But mostly, it was just hard to believe Soviet medicine could be as bad as its reputation.

It's worse, according to Inside Russian Medicine, which Dr. William A. Knaus has written based on personal experiences and observations, gathered during a year as physician to a traveling U.S. exhibition in the Soviet Union plus two short subsequent visits, and on excellent research of the popular and medical literature there by Nicholas A. Petroff.

This is the most comprehensive and best-documented general survey of Soviet medicine and its failings yet available. Its message is that the Soviet Union is no place to get sick, except if you are one of the Communist elite. (But for the reader who want to go there, Knaus has a 14-page appendix on "Taking Care of Yourself in the Ussr.")

Knaus, now co-director of the intensive care unit at George Washington University Hospital, was a minor hero in Moscow's Western community, including among embassy doctors, for having faced down Soviet authorities in Siberia in 1973 by insisting that an American patient of his be evacuated by a special U.S. hospital plane. The episode, retold in the first 50 pages of the book, is at times breathless and at other times naive, as are remarks he makes in the preface. "I was close friends with dozens of ordinary Soviet citizens, physicians, workers and students," he claims, apparently as unmindful of security clearances required for "ordinary" citizens to meet foreigners as he was unfamiliar with the language.

But the Siberian incident establishes him as a physician in the best tradition of his profession, and this provides important credibility in later chapters.

In a detached manner, Knaus described problems in Soviet medicine including the inadequate education of doctors, 70 percent of whom are women, and their low pay and status (tax drivers earn more); the hospitals, which are still known as "houses of suffering," thanks in part to their policy of admitting unsterile visitors to operating rooms; and research rural medicine, psychiatry and even Solzhenitsyn's vaunted self-cure of cancer.

Nothing better illustrated the state of Soviet medicine for me than the apteka, or drug store, with compartments covering whole walls in which hundreds of kinds of "grasses" were kept. These herbs make tea for whatever ails you, from anise for gas and dill for heartburn to geranium root for internal bleeding. Because of the lack of modern drugs, Russians have not come far from their village past. Knaus reports that one of Moscow's best hospitals stocks eight kinds of antibiotics, of which only four are routinely available, compared to 67 at George Washington University Hospital.

The life expectancy in Russia at the time of the 1917 Revolution was 30 years, the same as in Colonial America in 1750. Draconian public health measures, and the determined output of doctors and hospital beds (twice as many per capita now as in the United States, in both cases), enabled the Soviets to improve rapidly upon that figure.

In 1970, the U.S.S.R's infant mortality rate, an excellent index of a nation's overall health, began rising dramatically. Murray Feshbach, of the Census Bureau's foreign demography division, was first to note that the infant death rate rose 22 percent by 1974, when the Soviets simply stopped publishing those statistics. Feshbach estimates that the rise continued at least until 1976, reaching at least 31 deaths per 1,000 live births, or twice the U.S. level.

"Today, Soviet health indices resemble those of a developing rather than a developed country. Clearly something is wrong," Knaus writes in the kind of understatement typical of much of the book. In fact, if the Soviet Union were a weak African nation, an international relief effort might be called for.

This tragedy is blamed on rampant alcoholism among women as well as men, and a staggering level of abortions which often harm the woman and subsequent children. The average Soviet woman has six abortions during her lifetime. Sixteen million abortions per year, more than 10 times the U.S. total, are performed in the U.S.S.R., outnumbering births four to one. There are high rates of postoperative infection.

Knaus also notes that rural Muslim regions as well as Russian cities have high infant death rates. Rickets, eradicated in most countries with Vitamin D, accounts for 37 percent of infant deaths in rural regions, he writes.

Surgeons are bribed to insure that they, rather than their apprentices, perform operations. Narcotics nurses are bribed to insure injections are given on time. Druggists are bribed to get commonly prescribed but unavailable drugs. These bribes (which Knaus refers to, perhaps out of professional courtesy, as "informal service charges") "make the much publicized Soviet claim of besplatno (free of charge) and inexpensive hospital care less absolute," he writes.

Knaus is too reluctant to criticize the political system that pervades and corrupts Soviet medicine, as well as every other scientific field. More money would improve health care, he writes, but then adds that money alone is not enough to reverse the educational and institutional failings. He repeats the canard that "you can't be a good Communist and a good doctor," but immediately admits it is too broad and harsh a verdict.

By shunning politics, Knaus diagnoses the illness, as it were, but shies away from prescribing the cure. Soviet medicine obviously needs the same kind of fundamental overhaul that American medicine underwent almost a century ago. Knaus' views on reform would have made a valuable final chapter. But this does not reduce the importance of the book in exposing the scandalous deficiencies in Soviet medicine.